This invention relates to rotating devices and, more particularly, to apparatus for applying a controlled braking force to such a rotating device while at the same time preventing the device from rotating in a reverse direction.
In the prior art, in order to prevent reverse rotation of a device such as a drum, a pawl and ratchet combination commonly has been utilized. The use of a pawl and ratchet combination has its drawbacks, however. In particular, in a device such as a facsimile transceiver utilizing a rotating drum for document transport, for example the 400 Telecopier transceiver unit manufactured by Xerox Corporation, reverse rotation of the drum therein can cause serious damage to, or destruction of, the stylus used for writing. The use of a pawl and ratchet to prevent reverse rotation still allows enough reverse rotation to damage the stylus. Another problem peculiar to facsimile transceivers is that the pawl and ratchet combination does not prevent jitter in the transmitted copy.